This invention relates to a down hole assembly used to clean tubular strings. More particularly, but not by way of limitation, this invention relates to an apparatus and method for cleaning the internal diameter of casing strings with a bristle brush circumferentially arranged about a down hole assembly.
In the development of oil and gas fields, operators will drill a well to a hydrocarbon reservoir, and thereafter, run a casing string through the production formation. The casing string will then be cemented into place. In turn, the well will then be completed as is well appreciated by those of ordinary skill in the art.
The optimization of production is an important criteria of any completion. Studies have shown that residue on the internal diameter of the casing string (such as cement, pipe dope, scale, burrs, et cetera) have a negative impact on productivity. Specialized completion fluids devoid of fines, solids and other debris are used to complete the well. Therefore, a major emphasis has been made to clean the inner diameter of the casing string.
Thus, when the operators have finished the pumping of a cement composition through the well casing, a work string is lowered on which a mechanical scraping device is used to scrap the walls of the casing. In the prior art, various types of casing scrapers are in use prior to displacement of a clean completion fluid. That is why it is so important to clean the casing wall as much as possible since it takes less time to ultimately filter the displaced completion fluids. Also, cleaning will eliminate foreign matter such as cement sheaths, scale, burrs and barite which in turn allows the tools used in the completion process to properly perform.
The scraping action of traditional scrapers with blades also have been known to leave a fine film of oil base or synthetic fluid residue on the casing wall. Prior art devices also cause problems because of the hardness of their blades cannot get into the casing connections as brushes can. Also, casing scrapers in high deviated holes collapse to the low side of the casing causing a great deal of wear on one side and the top side of the hole is not properly cleaning the high side due to ineffective engagement with the high side.
Therefore, there is a need for a down hole assembly that will be effective in cleaning a well bore that contains an oil base and/or synthetic fluid. There is also a need for a cleaning apparatus that will be effective in highly deviated wells. There is also a need for a down hole assembly that will have brush pads that are of sturdy construction and allow for ease of replacement.
A down hole cleaning assembly is disclosed. Generally, the down hole assembly is connected to a work string concentrically located within a casing string. In one embodiment, the down hole assembly comprises a mandrel operatively connected to the work string, with the mandrel having an opening therein. A pad member is received within the opening, with the pad member having a groove formed therein. Also provided is a wire brush means, operatively positioned within the groove of the pad member, for cleaning the internal diameter of the casing string.
The down hole assembly further comprises a biasing member, operatively positioned between the mandrel and the pad member, adopted for biasing the wire brush means against the inner diameter of the well bore. In the preferred embodiment, the wire brush means comprises a wire bundle having a first end and a second end, a brace disposed about the second end of the wire bundle, and wherein the brace is disposed within the groove of the pad member.
The brace herein disclosed includes an open end and a closed end, with the closed end having disposed therein the second end of the wire bundle, and wherein the open end and the closed end cooperate to form a triangular shaped profile. The groove will also contain a triangular shaped profile adapted to slidably receive the triangular brace.
In the preferred embodiment, the mandrel contains a second of slot, and wherein the down hole assembly further comprises a second pad member adapted to be received within the second slot, the second pad containing a second groove formed therein. A second wire brush means, operatively positioned within the second groove of the pad member, is also provided for cleaning the internal diameter of the casing string.
The down hole assembly may also contain a centralizer means, operatively adopted to the work string, for centralizing the mandrel within the casing string. A dove tail means, operatively associated with the mandrel, is also included for selectively adapting the wire brush means onto the work string.
In the preferred embodiment, the first and second wire brush means are arcuate, and wherein said first wire brush means is disposed about the periphery of the mandrel to cover a first 180 degree phase and wherein the second wire brush means is disposed about the periphery of the mandrel to cover a second 180 degree phase so that the first wire brush means and the second wire brush means cover a 360 degree phase about the mandrel. In another embodiment, a plurality of wire brush means may be placed about the periphery of the mandrel, with the wire brush means being staggered circumferentially in relation to each other so that the wire brushes have an effective coverage area of 360 degrees.
Also disclosed herein is a method of cleaning a casing string. The method comprises lowering a work string within the casing string. The work string will have provided therewith a down hole cleaning apparatus operatively associated with the work string. The wire bundle of the cleaning apparatus will be urged against the inner diameter of the casing string via the spring to allow for constant pressure of the brushes against the casing wall at all times. The method provides for cleaning the inner diameter of the casing string as the work string is lowered.
The method further comprising rotating the work string, and thereafter, lowering the work string. The operator may then circulate a drilling fluid through the inner diameter of the work string. The work string may be stationary or rotating during circulation.
In one embodiment, the well casing has a horizontal section so that a low side of the well casing and a high side of the well casing is created. In this embodiment, the apparatus includes a centralizer operatively associated with the work string. Also included will be a second cleaning apparatus, with the first cleaning apparatus covering a 180 degree phase and the second cleaning apparatus covering a complimentary 180 degree phase so that the entire 360 degree periphery is covered.
The method would further comprise lifting the apparatus from the low side of the inner diameter of the well casing with the centralizer. Also, the wire bundle of the first cleaning apparatus is urged against the low side of the inner diameter of the well casing with the spring at a constant force. Simultaneously therewith, the wire bundle of the second cleaning apparatus is urged against the high side of the inner diameter of the well casing with its spring at a constant force so that both the low side of the casing and the high side of the casing will be cleaned.
In a second embodiment, an apparatus for cleaning an inner diameter of a casing string is disclosed. In this embodiment, the down hole assembly comprises a mandrel having a first end and a second end, with the first end of said mandrel being configured to be connected to an opened end of a first tubular member and the second end of the mandrel being configured to be connected to an opened end of a second tubular member. The mandrel contains a first helical opening.
The apparatus further contains a first helical pad configured to be positioned within the first helical opening, with the helical pad having a groove therein. A wire brush member is inserted within the groove and a first spring is inserted between the first helical pad and the mandrel, with the spring biasing the helical pad radially outward.
The apparatus further contains a dove tail means, operatively associated with the mandrel, for selectively adapting the first second helical pad member with the mandrel. The dove tail means comprises the first tubular member having an opened end with an annular ring formed thereon that engages a first lip extending from the first helical pad, with the first lip being configured to adapt to the annular ring so that the first helical pad is held in place by the annular ring.
The apparatus further comprises a second helical opening formed on the mandrel and a second helical pad configured to be positioned within the second helical opening. The second helical pad will have a series of annular ribs disposed thereon. A second spring is inserted between the second helical pad and the mandrel, with the second spring biasing the second helical radially outward. In this embodiment, the dove tail means further comprises the second tubular member having an opened end with an annular ring formed thereon that engages the first lip so that the second helical pad is held in place by the annular ring.
The apparatus may further comprise a third helical opening formed on the mandrel, with the third helical pad being configured to be positioned within the third helical opening. The third helical pad contains a series of annular ribs. A third spring is inserted between the first helical pad and the mandrel, with the spring biasing the helical pad radially outward. A fourth helical opening may also be included, with a fourth helical pad configured to be positioned therein. The fourth helical pad will have a series of annular ribs. A fourth spring is inserted between the second helical pad and the mandrel for biasing the fourth helical pad radially outward.
In the preferred embodiment, the wire brush member comprises a wire bundle having a first end and a second end, a brace disposed about the second end of the wire bundle, and the brace is disposed within the groove of the pad member. The brace comprises an open end and a closed end, with the closed end having disposed therein the second end of the wire bundle, and wherein the open end and the closed end cooperate to form a triangular shaped profile. The groove will also have an angular shaped profile adapted to slidably receive the wedge of the brace. The first and second wire brush members will be arcuate. In one embodiment, the first wire brush member is disposed about the periphery of the mandrel to cover a first phase and wherein the second wire brush member is disposed about the periphery of the mandrel to cover a second phase.
A method of cleaning a casing string with this second embodiment is also disclosed. The method comprises lowering a work string within the inner diameter of the casing string and providing a cleaning apparatus operatively associated with the work string. The method includes urging the wire brush member against the inner diameter of the casing string with a first and second spring biasing a helical pad member and cleaning the inner diameter of the casing string. The method further comprises rotating and lowering the work string. A fluid may be circulated through the inner diameter of the work string which in turn will cause the fluid to be returned on the annulus side, with the fluid being channeled between and through the helical pad.
In one embodiment, the well casing has a highly deviated section so that a low side of the well casing and a high side is created, and the apparatus further comprises a centralizer operatively associated with said work string, with the first helical pad covering a first phase and the second helical pad covering a second phase. The method further comprises lifting the apparatus from the low side of the inner diameter of the well casing with the centralizer, urging the wire brush member of the first helical pad against the low side of the inner diameter of the well casing with said spring at a constant force and urging the wire brush member of the second helical pad against the high side of the inner diameter of the well casing with the spring at the constant force.
In a third embodiment, which is the preferred embodiment of this application, a down hole assembly is disclosed. The down hole assembly comprises a mandrel having a first opening, with the first opening having a first lip. The mandrel also includes an indentation. A first wire brush is inserted into the first indentation. A first spring is positioned between the first wire brush and the first indentation, with the first spring biasing the first wire brush outward. The mandrel also includes an aperture.
The assembly further contains a first sleeve disposed about the mandrel, with the first sleeve engaging the first wire brush member. A first locking dog is disposed in the aperture so that the first end of the first locking dog engages the first sleeve.
The mandrel may further contain a second indentation, and wherein the assembly further comprises a second wire brush inserted into the second indentation. A second spring is positioned between the second wire brush and the second opening, with the second spring biasing the second wire brush outward. A second sleeve may be disposed about the mandrel, with the second sleeve engaging the second wire brush member. A second locking dog may be disposed in a second aperture in the mandrel, with the second locking dog having a first end engaging the second sleeve.
In the most preferred embodiment, the first and second locking dog comprises a cylindrical member having an external threads engaging an internal thread on the aperture of the mandrel, with the cylindrical member forming a chamber. In the preferred embodiment, a spring is contained within the chamber. The locking dog further contains a stem having a shoulder thereon, with the stem engaging a depression in the first and second sleeves.
In one embodiment, the first wire brush and the second wire brush comprises a wire bundle and a brace disposed about a second end of the wire bundle, and wherein the brace is disposed within a groove in the pad member. The brace may have a closed end having disposed therein the second end of the wire bundle, and wherein an open end of the brace and the closed end cooperate to form a triangular shaped profile.
In one embodiment, the groove has an angular shaped profile adapted to slidably receive the triangular shaped profile of the brace. Additionally, in one of the embodiments, the first opening and the second opening are helically shaped, and wherein the first and second wire brush members are helically arranged. In still another embodiment, the first and second wire brush members are arcuate, and wherein the first wire brush member is disposed about the periphery of the mandrel to cover a first phase and wherein the second wire brush member is disposed about the periphery of the mandrel to cover a complimentary second phase.
Additionally, in one of the embodiments herein disclosed, the sleeve contains a series of spiral blades for centralizing the mandrel in the inner diameter of the casing string. Further, a centralizer may be formed on the mandrel for centralizing the mandrel in the inner diameter of the casing string.
A method of cleaning a casing string with the third embodiment is also disclosed. The method comprises lowering a work string within an internal portion of the casing string. A cleaning apparatus is attached to the work string, with the apparatus comprising: a mandrel having an opening, with the mandrel having an aperture therein, and wherein the opening has a first lip; a wire brush inserted into the opening; a spring positioned between the wire brush and the opening, with the spring biasing the wire brush outward; a sleeve disposed about the mandrel, with the sleeve engaging the wire brush; a locking dog disposed in an aperture disposed on the mandrel, with the locking dog having a first end engaging the sleeve.
The method includes urging the wire brush member against the internal portion of the casing string with the spring and cleaning the internal portion of the casing string. The method further includes rotating the work string and lowering the work string. A fluid is circulated through the internal portion of the work string, with the fluid being channeled through the wire brush pad in the annulus area.
In one embodiment, the well casing has a highly deviated section so that a low side of the well casing and a high side is created. The apparatus further comprises: a second wire brush member inserted into a second opening in the mandrel; a second spring positioned between the second wire brush member and the second opening, with the second spring biasing the second wire brush outward; a second sleeve disposed about the mandrel, the second sleeve engaging the second wire brush member; and, a second locking dog disposed in a second aperture, with the second locking dog having a first end engaging the second sleeve; and a centralizer operatively associated with the mandrel, with the first wire brush pad covering a first phase and the second wire brush pad covering a second phase. In this embodiment, the method includes lifting the apparatus from the low side of the inner diameter of the well casing with the centralizer. The first wire brush pad is urged against the low side of the inner diameter of the well casing with the spring at a constant force and the second wire brush pad is urged against the high side of the inner diameter of the well casing with the spring at the constant force.
An advantage of the present invention includes the ability to thoroughly clean the internal diameter of the casing of a course material such as cement while at the same time being able to scour the casing of thin films left by oil base and synthetic muds that contain hydrocarbons. Another advantage includes that the design allows easy replacement of the components so that if a brush becomes worn, a new brush may be easily inserted therein at the rig location.
Another advantage includes use of wire bristles that are of sufficient hardness to allow for the scraping of the inner diameter of the casing. Yet another advantage includes a staggered configuration of the brushes that allows for the entire 360 degree periphery of the casing to be cleaned with the upper set of brush pads or upper scrapers pads. Another advantage is that the staggered configuration of lower scraper pads or lower brush pads that allows for the entire 360 degree periphery to be cleaned. Still yet another feature is that the device may be used in highly deviated and/or horizontal wells.
An advantage of the present invention is that the helical pad allows for channeling of well bore fluid in the annulus area. Another advantage is that the helical brushes and scraper pads (also referred to as ribs) allow for better cleaning of inner diameter of casing string. Yet another advantage is the scraper pads, and brushes are interchangeable with each other.
Another advantage is that the novel locking mechanism allows for the locking of the brush pads without the need for make up via traditional thread means. Another advantage is that the mandrel can be forged from a single stock which will make the apparatus stronger in application. Still yet another feature is the novel locking dog"" use with the cleaning pads which allows for ease of manufacture and use. This embodiment does not require torquing of the mandrel, and therefore, this gives the advantage of having a stronger tool since the torquing process may weaken the assembly in repetitive use, over torquing, etc.
A feature of the present invention includes a novel locking mechanism brace that allows the clamping of a bundle of wire bristles. Another feature is that the novel locking mechanism includes triangular grooves formed within the pad that cooperate with a triangular brace profile fitted therein. Yet another feature is the dove tail locking means for selectively locking the pad onto the mandrel.
Another feature includes a spring loaded pad that urges the wire brush against the wall of the casing at a constant pressure. Thus, in a highly deviated well, both the high side and low side of the well will be cleaned. Still yet another feature is use of a centralizer that allows for the wire brush to be centered within well. This feature keeps both brushes centralized which in turn keeps the same pressure about the circumference of the casing walls.
Still yet another feature of the present invention includes use of helical brushes inserted into a helical pad. Another feature is the helical ribs that act to clean and centralizer the tool in a well bore. Yet another feature is that in one embodiment an upper row of helical brushes is used and lower row of helical ribs (also referred to as scraper pads) is used. Still yet another feature is that sleeves may serve as a centralizer.